Phonodyne



Sept. 11, 1928.

1,684,129 E. HOPKINS PHONODYNE Filed March 18, 1922 Fig. 6

Inventor:

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Patented Sept. 11', 1928.

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Application ma 1mm is, 1922. Serial No. 544,928.

The vmain object of myinvention is to produce sound from sound records,i n approximately the volume and purity of t original, particularly for use in talking mo- 5 tion pictures.

Heretofore sound recording has been effected in the form of a single track recordfrom a single dia hragm, but as sounds to be recorded are of great variety of volume,

pitch and timbre the records have proven defective. v r.

The basic principle of my invention is to divide the sound into a lurality of frequencies-and to record each frequency on a separate track, or to merge a number of such frequencies into a confluent band and record such band on its own track. Each record is thus a component part of the whole band of frequencies. This method is distinct from that of recording each note ofa composition on a separate track, since each note contains not only its own frequency but also its partials, or overtones. By my method such overtones may occur on a track separate from the track on which the fundamental is recorded. H

The speech and musical frequencies usually recorded range from 100 to 3500 vibra- 'tions per second. 'Miisical tones are not pure but have numerous overtones orpartials and voice effects are lesspure. The characteristic timbre of a note depends on the relative force of the fundamental and partials and their relative attenuation of density in the wave. A pure note without partials, A for example, has 435' vibrations per second, that is to say 435 nodal strata oc.-' cur per second. The density of the wave between the densest part of the nodal strata :and. the thinnest part of the ventral strata attenuates uniformly but when artials and discords are introduced the uniform attenuation is varied and a tone, characteristic of a certain instrument may maintain its density for a considerable time and then pass rapidly into the strata of rarefication, while another instrument may produce a tone that rarefies rapidly. .In one case at of a wave length from the nodal stratum the .0 density may be 90% of that at the nodal 1 stratum, while in the other the density may have drop ed to 20%. 'Such variations in what may e termed the modulus of density determine the characteristic timbre of the sound and identify the person or instrument singing The mam purpose of this invention is to select simultaneously various stages of vibration and record them independently. As"

given only a faint amount of the ener forth can be utilized in recording it comes possiblewith separately recorded frequency stages to amplify each one to a moderate degree and thus produce a considerable augmentation of sound without subjecting the' be multiplied.

Professional musicians are able to distinguish a discrepancy of two vibrations per second in the treble clef where the notes differ by about .30 vibrations per second, that is to say of a half tone. But most hearers cannot notice any discrepancy until it reaches four vibrations er second or about of a half tone. t is sufiicient, therefore, for lpractical purposes to select ten stages per ha ftone, or 120 per octave, or

600 for the five octaves customarily used. It

is more desirable to have two series ofselectors, 300 in each series, of a half tone apart, overlapping each other,by fifty per cent. The stage selectors may assume various forms, an excellent form being the Helmholtz resonator, a' spherical body with polar apertures, which selects certain tones and also augments them.

While the best result 'is obtained when the number of tone or stage selectors equals the number of frequencies such an apparatus i-sexpensive and bulky, and stage selectors having a wider range may be employed as those with wider range may be. fewer innumber. The sharpness of tuning of Helmholtz resonators depends on the size of their orifices. A largeorifice enables the resonator to-cover a greater range of vibrations. larger range and a resonator slightly flared A tubular resonator covers a. still highly desirable result several hundred frequencies should be selected.

To reduce the cost a highly useful pro cedure within the invention is to re-integrate cups of such frequencies into confluent finds from eight to twenty in number, and produce a record with from eight to twenty separate tracks. Again this is not s1m1lar to a phonograph in which half an octave of notes may be included on one track, since, for example, a note whose fundamental is on the lowermost track may have sixteen or more overtones or partials which will be distributed amongst most of the tracks above. One resonator will accept the fundamental but reject most of the overtones while other resonators will accept the various overtones.

It is also within the practice of the invention to permit certain frequencies to be lost. Thus if a bank of resonating tines be provided as stage selectors, their sympathetic vibrations will cover the range of fre quencies at certain points only, but if such gaps are not too wide the ear will not perceive the loss. Where the musical instrument or voice sings exactly on pitch, a resonator for each note or 12 per octave would be sufiicient, but for the speaking voice which has the closest of intervals it 6 is best'to have a bank of resonators somewhat overlappin so that as the frequencies begin to be lost in one they begin to appear in the next. nipulation of the apparatus it is possibe to lose certain frequencies or augment others and alter the characteristic timbre of sounds purposely, smoothing out, for example, a wolf note in a violin or a hoarse quality in a voice.

It is of course obvious that not all the resonators are constantly employed. If the tones are all on the upper notes the lower resonators will be idle.

In carrying out my invention I find it desirable to employ the following apparatus, processes and manufactures, but it is to be understood that less than all of the different means, mechanisms, processes and manufactures herein described may be employed, or parts only may be employed, or

other means, mechanisms, processes and- By a suitable selection or masame reference letters and numerals indicate the same or corresponding parts:

Figs. 1 to 6 illustrate a form of the invention in which the differentiation of the means and the recording by electrical means.

Fig. 1 is a plan of the apparatus;

I Fig. 2 is a side elevation;

Fig. 3 is a portion of the front elevation; Fig. 4 is a sectional rear elevation on line A of Fig. 2;

Fig. 5 is a diagram of arrangements and connections Fig. 6 is a diagrammatical plan ofv a record recorded by the apparatus.

Figs. 1 to-4 illustrate a restricted form of the apparatus. Three units are shown but the number may be very much greater if desired. A number of horns are provided, the fronts of which are covered, admission of sound to the horns being by means of Helmholtz resonators 1 to 9. -Horns 10, 11, 12' are mounted in front wall 30 and supported by standards 16, 17, 18 on base plate 35. The horns are pyramidical, of rectangular cross section to save space, but may be of conical or other form. Covers 32, 33 and 34 cover the front ends of the horns and support the resonators. Cover 32 carries resonators 1, 4, 9, cover 33 carries resonators 2, 5, 7 and cover 34 carries resonators 3,

Considering resonator 1 v, as capable of selecting pitch C5 or 1024 vibrations per second, resonator 7 would select pitch C3 of. 256 vibrations e1" second and resonator 9, C2. or 128 vib sizes are merely -approximate. The illustration of three resonators per horn is merely for convenience in drawing, as the number may be greater or smaller, or only 7 a single resonator maybe used per horn, or

The effect of the a for some of the horns. Helmholtz resonators is to more or less completely exclude from admission to the horn all the frequencies which are not selected by the resonator and to deliver to the interior of the horn in amplified form' the frequencies selected by the resonator. The sound waves enter the resonators through mouths 31 and pass into the ,horns through stems 38. It will be seen that small resonators are attached to horns carrying large ones.

In order to further augment the sound acting on the diaphragms tubular resonators are applied to the horns. Tubular resonators 21, 24, 29 are afiixed. to horn 10;

rations per second. -The' frequency stages is effected by physical to 2000 vibrations,

' second overtone onthe and its 2560 vibrations per second, overtone all three scion bands sim holtz resonators horns.

tubular resonators 22, 25, 2'! to born 11- and tubular-resonators 23, 26, 28-t0 born 12. These tubular resonators preferably res 0nd to the same pitch as corresponding elmaflixed to the fronts of the flu case a horn is on y elm oltz resonators of almost the same pitch to it. Thus if the singer ets slightly off pitch the sound is not lost. ior singingrecording thus some horns with a Helmholtz resonator at each pitch of the tempered scale may sufiice, supplemented by resonators at very nearly the same pitches. A further useful feature of'my invention is to clarify the sounds in" the horn by nodal apertures as 36. Wherever the node of a frequency or overtone is found in a horn, such frequency may be greatly diminished if not entirelydissipated y lacing a small hole at the nodal point. Wll been placed in a single recording horn to improve its recording qualities, it 15 a novel feature of'my invention to place a plurality of holes in a set of recording horns for the purpose of differentiating or selecting freuencies for recording, in such a manner t at frequencies dissipated from one or more horns are preserved in one or more others. Thus two long horns may be provided with nodal apertures so arranged that certain frequencies dissipated on one are preserved on the other, a two track record thus being suflicient; while three or more horns may be arranged with nodal apertures in suc relation as to both dissipate the natural fre-. uencies of the horns as well as differentiate into scion bands the total fre uencies making up the whole record. Wit in the invention may thus be found ready means of dividing the-frequency band into any de-. sired number of scion or component bands. Should "thewhole band of frequencies be divided into three scion bands, the lowest scion band might range from 100 to 1000 vibrations, the middle scion band from 1001 and the upper scion band all vibrations above 2001 per second. Or the scion bands or stages might be caused to overlap, the first running from 100 to 1050, the middle from 1000 to 2050 and the third from 2000 upwards. Thus a note or tone having 640 vibrations per secon would have its fundamental recorded on the lower scion band, its 1280 vibrations'per middle scion band on the upper scion band, provided. such tone had such overtones. Any other overtones it'might have would be recorded on the suitable scion ltane'ously would then be necessary to reproduce the note or tone correctly, as part of its timbre would be to record one fre-- uenc it is oftendesirable to attach several tubular resonators may.

horns without the other resoile holes have of light are more or less band. Reproduction from be. v

A series. of slips is cover oblon'gholes inhavin' round apertures the exact ocation of thus be varied. w r x Three means of differentiating are illustratedin Figs. 1 to 4. The Helmholtz'reso nators may be employed without horns by attaching diaphragms to their stems,

be employed similarly or on the nators, in which case the particular pitches they represent will be greatly augmented so that the non-augmented pitches will but slightly influence the recording diaphragm, or if it is still may 'fail to influence it; and the nodal aperture method alone may be used. Any two of the said meansmay be employed together, but i iisdesirable to use all three together. The location of the tu-v bular and Helmholtz resonators may be valost should' one two of the scion I S awn as animal the horn body, while, j

mselves. The'] the nodal aperture may ried. The tubular resonators may have open or closed ends as circumstances of pitch and struments.

Diaphragm boxes 13, 14 and 15 are attached to the ends of horns 10, 11, 12. It is desirable to have the natural frequency of the diaphragms below that of the frequencies to be recorded. But if Helmholtz resonators are used singly the diaphragm is best of the same frequency as the resonator.

The horn diaphragms are fitted with small mirrors-37, '38, 39, a well known means in the art for reflecting rays ofv light from sound recording diaphragms. Table 40 supported by legs 19, 20 carries a source of light 41 which is adapted to shine on the mirrors as shown by lines 42, 43, 44. The mirrors are arranged to reflect the light on lines 45, 46, 47 to photo-electric cells 51, 52. Lines d 49 and 50 indicate the direction of "rays to and from another horn not illustrated.

Placed before photo-electric cells 51, 52

are screens53, 54. w"ith slots 55, 56 and 5?,

58, respectively. When, the mirrors are agitated by sound waves in the horns the beams defiectedgand when normally arranged to fall on the screens are more or lessdeflected onto the photo-electric' cells. As is well known small changes of electric conductivity are caused in photoelectric cells by changes in light falling on the original them. Thus loud sounds in the horns throw more light onto the cells, and the electric variations thus produced are utilized for making the actual sound record. One light source, it will be seen, is used to furnish illumination for all the mirrors. This source .of light should be steady.

Fig. 5 shows a diagram of connections. Twelve horns are indicated, 59 to inclusive. Light source 71 throws rays of light onto all the mirrors as indicated by dash lines, as,72. Photoelectric cells 73, 74, receive reflected light from the mirrors as indicated by dotted lines, as 76. Cell 73 receives reflected light from horns 59, 60,

61 and 62; cell 74 from horns 63, 64, 65,

66 and cell 75 from horns 67, 68, 69, 70. (Fell 74 is placed on a slightly lower level than light 71 in order not to cause interference of light rays, the mirrors being tilted accordingly. Cell 74 is further from the mirror than cells 73, 75, but the combined length of the original light path to the mir I'Ors and the reflected path from the mirrors to the cells is approximately the same, in each case, a desirable condition. It is within the invention to use photographic means for recording light variations, well known in the art, instead of the means shown, but

I prefer to use the method of the photo electric cells shown as being more sensitive and less cumbersome than 'the other meth ods. Itis to be noted that the invention includes the secondary integration illustrated. The various frequenc stages are firstintegrated in the group 0 horns, and then a group of horns is integrated in a photoelectric cell. The current from all the cells may further be integrated into a single current if desired and a single track record luade therefrom. Such a record is.vastly more accurate than one made from a single diaphragm as the electrical variations are without inertia and every characteristic of sound is represented in the record. a

Formany uses, however, I prefer a multiple track record, each track with its own scion band of merged or confluent pitches or frequencies, merged in the first instance by horns and in the second by photo-electric cells, or. progressively confluent.

Photo-electric cell 75 is connected in circuit with battery 77, magnet 82 and amplifier system, which may be of the audion type, 78. Variations in the light thus alfect the intensity of the magnet field. A steel tape 84 is impressed with such variations in the manner of the Poulsen telegraphone. Photo cell 73 influenced by horn mirrors 59, 60,

61, 62 controls magnet through battery 79 and amplifying system 83. Cell 74 influenced by horn mirrors 63, 64, 65, 66 controls magnet 81 through battery 79 and amplifying system 83. Two sets of the magnets and cells are thus operated through one battery and amplifying unit. The amplifying system may be of the audion type, Alexanderson magnetic, Brown relay or any desired type.

The record is shown in Fig- 6. A steel band or ribbon 84 or band of magnetic metal is provided which passes the poles of the three magnets. The magnets thus impress on the magnetizable ribbon three tracks, 85. 86, 87. The dotted ortions represent portions moreimpressed with magnetism than the portions containing the dashes. Thus if the frequency stages of the original sound are divided into twelve parts and each of the three photo-electric cells re-integrates into a confluent band four of such parts, then each track represents one third of all the frequencies recorded. None of the three tracks will alone reproduce. the original sound or indeed, necessarily, any recognizable part of it, but on being reproduced in unison by means of suitable teleg'raphone reproducing apparatus the sounds of the three tracks Will coalesce in the air and reproduce the original sound.

At 88, 89, 90, 91 are shown apertures in the ribbon. These are sprocket feed holes to enable the speed of the ribbon to be ex actly controlled in connection with a motion picture camera for talking motion pictures. It is novel to place such feed holes away from the edges of the ribbon. Ribbon 84- 92 is shown separate from ribbon 93 87,

1. The process of'sound recording which comprises transforming the air waves into vibrations in another medium, in selecting from such vibrations a lurality of stages and in recording each 0 said stages independently.

v2. A sound record of a band of sound frequencies comprising a plurality of members each of which is a record 0 a co1npo nent part of the whole band of frequencies.

3. A sound record of a band of sound frequencies comprising a plural'ty oftracks in a single member, each of which tracks is a record of a component part of the whole band of frequencies.

4. The process of mak ng sound records which'comprises transforming the original air waves of the sound into vibrations in another medium, in selecting from such vibrations a plurality of stages, in integrating bands of said stages into confluent stages, and in recording independently such confluentstages.

5. .A sound record of a band of sound frequencies comprising a plurality of members,-

each of which is a record of an integrated confluent stage of scion band frequencies.

6. A sound record of a band of sound frequencies comprising a plurality of tracks in quencies comprising a plurality of tracks on a single mom er, each of which is a physical record of physical vibrations of integral stages ofv the whole band of frequencies.

9. The process of making a multiple member sound record of a band of frequencies which comprises selecting a plurality of stages of such frequencies, in integrating groups of such stages, .in producing from eachof such groups hysical vibrations and in recording such vibrations each in an independent member of the record.

10. The process of making a multiple member sound record of a band of sound frequencies which comprlses selecting a plurality of stages of such frequencies, in integrating groups of such stages, and in producing from each of such groups physical vibrations and in recording such vibrations each in an independent track of the record.

11. The process of making a sound record of a band of sound frequencies which comrlses selecting a plurality of stages of such requeneies, in integrating groups of such stages, in producing from each of such groups physical vibrations, in deriving elec trical vibrations from such physical vibrations and in recording such electrical vibrations on independent members.

12. The matter of claim 11 when the integrated groups of vibrations are recorded each in a separate track of a multiple track record.

13. The matter of claim 11 when the integrated groups of vibrations are recorded each in a separate track of a multiple track magnetic record.

14. A multiple member sound record of a band of frequencies comprising a plurality of members each of which contains an integral stage of the Whole band of frequencies, such stages derived from electrical vibrations produced by confluent light vibrations from a group of stage selectors.

15. A. multiple track sound record of a band of frequencies comprising a plurality of tracks on one member, each of which tracks contains an integral stage of the Whole band of frequencies, such stages derived from electrical vibrations produced by confluent light vibrations from a group of stage selectors.

16. A sound recording apparatus comprising means for dividing the sound frequencies into bands or stages and means,for recording such bands or stages independently.

17. A sound recording apparatus comprising means for dividing the sound frequencies into bands or stages and meansfor recording such bands or stages each on a separate track of a sound record having a plurality of tracks in one member.

. 18. A sound recording apparatus comprising means for dividing sound frequencies into bands or stages, means for integrating groups of such bands or stages into confluent stages, and means for recording such confluent stages independently each on an independent member.

19. The matter of claim 18 when the con fluent stages are recorded on a sound record having a plurality of tracks, one for each of such confluent stages.

EDWIN HOPKINS. 

